Four Rio Tinto staff will go on trial in Shanghai tomorrow accused of bribery and stealing industrial secrets, even as the mining company increases its efforts to build bridges with the Chinese authorities.

The four were arrested in July and although initial charges claiming they were trying to obtain Chinese state secrets were later modified, the three-day trial is likely to heighten tensions between Beijing and the west.

In particular, the Australian government has voiced anger because one of the four is an Australian national, Stern Hu, who was in charge of sensitive iron-ore price negotiations between China and global producers. The four have been accused of seeking industrial and production information about Chinese mines and steel mills, and using that information as a bargaining chip to drive up the price that China pays for iron-ore imports.

The trial is expected to be held behind closed doors, with Australian diplomats excluded from some of the proceedings and foreign journalists barred altogether.

The arrests came a few weeks after Rio turned down a huge investment offer from Chinalco, China's state-owned aluminium group, which holds nearly 8% of the company and wanted to more than double its shareholding. Instead, Rio decided to raise funds via a rights issue and to set up an iron-ore joint venture with its rival BHP Billiton. Some in the City believe the two events may not be unconnected.

Rio, however, has not let the trial hamper its efforts in China, which is a key partner for global mining groups. Rio's chief executive, Tom Albanese, was reportedly in China at the weekend on a charm offensive, his second visit in a month, and on Friday Rio announced a deal with Chinalco on an iron-ore mine in Guinea that Rio has been hoping to develop for years.